U.S. Pat. No. 3,805,011 discloses a method and a tool for welding together two tubular members. One member has an enlargement at its end and integral therewith and which is positionable in register with a welding tip carried by the tool. The enlargement is heated by the tip to fuse or weld the same to the other member. In some cases, such as in nuclear power plant installations, it is desirable to use a weld metal that is different from the metal of the members being joined.